The invention relates to a blood transfer chamber.
Specifically, though not exclusively, the invention can be usefully applied in an extracorporeal circuit for performing an extracorporeal blood treatment, such as for example a dialysis treatment.
U.S. Pat. No. 5,503,801 teaches a bubble trap provided at a bottom thereof with a seating for housing a hollow truncoconical filter. On a lateral wall thereof, the filter exhibits openings which enable passage of blood while trapping larger particulate material of a certain size, such as blood clots and extraneous materials. Each opening substantially defines the same blood passage section.
U.S. Pat. No. 5,328,461 teaches a blow moulded venous drip chamber for hemodialysis in which a tubular blood filter is inserted, made of a plastic material. All the filter openings substantially exhibit the same passage section size.
Other examples of filters for a medical drip chamber are described in DE 3202582, GB 2028976, WO 81/01793, JP 2003/265601, JP 11290454, JP 8257114, DE 3143456, and JP 7299136. In these examples the lateral wall of the filter exhibits openings distributed essentially uniformly.
One of the drawbacks in the prior art is that the blood passage through the filter can cause hemolysis.
A further drawback in the prior art is the risk of stagnation of air bubbles in the upper part of the filter during the extracorporeal blood circuit priming stage. The priming stage, as is known, precedes the actual treatment. During the treatment the blood passes through the filter from the outside towards the inside, while normally during the priming stage a priming fluid (normally an isotonic saline solution) passes from the inside to the outside of the filter. During this priming stage any air bubbles contained in the priming fluid can be trapped internally of the filter, with the probability that they will then be sent on, during treatment, towards the outlet of the blood chamber, with the consequence that the air bubble sensor is activated, causing an alarm to be set off and hence blocking the treatment.